Glass compositions and fibers made therefrom

ABSTRACT

Glass compositions, having improved chemical resistance and useful in the form of fibers for reinforcing cementitious materials, consisting essentially of: 
     From 50 to 75 percent by weight Silica 
     From 10 to 25 percent by weight R 2  O 
     from .[.1.]. .Iadd.7 .Iaddend.to 15 percent Titania 
     From 1 to 20 percent by weight Zirconia 
     From 0.8 to 20 percent by weight Rare Earth Oxide 
     From 0 to 20 percent by weight Boric Oxide 
     From 0 to 10 percent by weight R 1  O 
     from 0 to 1 percent by weight Fluorine as (fluoride) 
     From 0 to 2 percent by weight Al 2  O 3   
     from 0 to 1 percent by weight P 2  O 5   
     from 0 to 1 percent by weight Chlorine (as chloride) 
     Where R 2  O is sodium oxide, potassium oxide or a mixture of both, optionally including up to 5% by weight of lithium oxide (based on the total composition) and R 1  O is MgO, CaO, BaO, or SrO, or a mixture of two or more thereof.

This application is a continuation-in-part of new earlier applicationSer. No. 441,984 filed Feb. 13, 1974, now abandoned.

BACKGROUND OF THE INVENTION

This invention concerns improvements in or relating to glasscompositions, fiber made therefrom and cementitious materials includingsuch fiber as reinforcement.

Glass compositions, containing beryllia, magnesia, strontium oxide,titania, cadmium oxide or zirconia have been known for many years (see,for example, U.K. Patent Specification Nos. 595,498 and 791,374 and U.S.Pat. No. 2,640,784). From these, refractory glass fiber and otherarticles may be made.

More recently, U.S. Pat. No. 2,877,124 discloses compositions which arechemically durable, have a low liquidus temperature and slowdevitrification and are capable of being formed into fibers by rotaryspinning and attenuation of the strands so obtained. These compositionscomprise, in weight percent;

    ______________________________________                                        SiO.sub.2            50 to 65                                                 Al.sub.2 O.sub.3     0 to 8                                                   CaO                  3 to 4                                                   MgO                   0 to 10                                                 Na.sub.2 O, K.sub.2 O, L.sub.2 O                                                                   10 to 20                                                 B.sub.2 O.sub.3       5 to 15                                                 TiO.sub.2            0 to 8                                                   ZrO.sub.3            0 to 8                                                   BaO                  0 to 8                                                   Fe.sub.2 O.sub.3      0 to 12                                                 MnO                   0 to 12                                                 ZnO                  0 to 2                                                   ______________________________________                                    

And preferably are essentially free from at least a majority of the sixlast-named components.

U.S. Pat. No. 3,127,277 discloses glasses of high modulus of elasticity,of composition, in weight percent:

    ______________________________________                                        SiO.sub.2         45-60                                                       CaO                9-19                                                       MgO                6-10                                                       BeO                7-12                                                       ZrO.sub.2         1-3                                                         Li.sub.2 O        up to 4                                                     TiO.sub.2          2-10                                                       CeO.sub.2         up to 4                                                     ______________________________________                                    

Optionally including other ingredients such as Fe₂ O₃ and Al₂ O₃.

U.S. Pat. No. 3,817,764 disloses glass compositions, in weight percent:

    ______________________________________                                        SiO.sub.2         49-57                                                       Al.sub.2 O.sub.3  3-5                                                         B.sub.2 O.sub.3    6-12                                                       Na.sub.2 O        18-20                                                       CaO               0-2                                                         TiO.sub.2          9-12                                                       ZrO.sub.2         0-7                                                         Fe.sub.2 O.sub.3    0-0.5                                                     LiO.sub.2         0-1                                                         ______________________________________                                    

and states that glass fibers which are especially water durable, and canbe made from these compositions by rotary or centrifugal spinning.

Finally, U.S. Pat. No. 3,861,925 discloses alkali resistant fiberizableglass compositions which are zirconia free and consist essentially of,in weight percent.

    ______________________________________                                        SiO.sub.2            55-65                                                    TiO.sub.2, La.sub.2 O.sub.2 or CeO.sub.2,                                                          12-25                                                    CaO                  4-6                                                      Na.sub.2 O,          12-18                                                    K.sub.2 O            0-3                                                      ______________________________________                                    

Despite such disclosures, however, there is still a need for glasseshaving improved chemical durability -- in particular improved resistanceto alkali attack, for example for use in reinforcing cementitiousarticles.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, a glass composition consistsessentially, by weight of the composition, of:

from 50 to 75% Silica

from 10 to 25% R₂ O

from .[.1.]. .Iadd.7 .Iaddend.to 15% Titania

from 1 to 20% Zirconia

up to 20% Rare Earth Oxide

from 0 to 20% Boric Oxide

from 0 to 10% R¹ O

from 0 to 1% Fluorine (as fluoride)

from 0 to 2% Al₂ O₃

where R₂ O is sodium oxide, potassium oxide or a mixture of both,optionally including up to 5% by weight lithium oxide (based on thetotal composition), and R₁ O is MgO, CaO, BaO or SrO, or a mixture oftwo or more thereof.

A preferred glass composition consists essentially, by weight of thecompositions, of:

from 50 - 58% Silica

from 11 - - % R₂ O

from 8 - 10% Titania

from 10 - 14% Zirconia

from 0.8 - 15% Rare Earth Oxide

from 0.5 - 4% Boric Oxide

from 0.1 - 6% R¹ O

from 0 - 1% Fluorine (as fluoride)

from 0.1 - 0.4% Chlorine (as chloride)

Wherein R₂ O is selected from the group consisting of Na₂ O, K₂ O andmixtures of the two and mixtures thereof additionally containing up to1% by weight lithium oxide (based on the total weight of thecomposition) and R¹ O is selected from the group consisting of MgO, CaO,BaO, SrO and mixtures of two or more thereof.

The compositions preferably comprise at least 20% by weight of ZrO.sub.2 and TiO₂ together, and at least 23% by weight of ZrO.sub. 2, TiO₂ andrare earth oxide together.

The composition preferably contains not more than 30%, and morepreferably not more than 25% by weight, of titania and zirconiatogether, and not more than 7% by weight of R¹ O. The R¹ O and F may bedeliberately added to the composition, within the ranges of contentstated above. If Li₂ O is used in place of fluorine then comparableamounts of Al₂ O₃ will be added (necessarily but not desirably) by wayof the raw materials commercially available at present. Al₂ O₃ shouldnot exceed more than 2% by weight of the composition.

The inclusion of a rare earth (metal) oxide imparts to the glasscompositions of this invention a degree of alkali resistance not, ingeneral, exhibited by glass compositions of otherwise similarformulation. At least 0.8% rare earth oxide is present in thecomposition.

The rare earth oxide used may be any of the naturally occurring ones,preferably ceric oxide, or a mixture of naturally occurring rare earthoxides. The term "naturally occurring rare earth oxide mixture" is wellrecognised in the Art used in the following examples according to itsaccepted meaning denoting a mixture of rare earth metal compounds(mainly the oxides) in which such metals are present in relativeabundancies approximately equivalent to their naturally occurringrelative abundancies. Such mixtures are constituted by, for example, anatural rare earth ore such as bastnaesite or monoazite; the term isalso used as herein to denote such an ore which has been treated toremove undesirable components such as carbonate, phosphate or fluorideions. When bastnaesite, for example, is treated to remove such ions, therare earth metal content remains constant, and remains proportional tothe naturally occurring abundance.

The detrimental effect of excessive amounts of certain ions, such asphosphate or fluoride, in glass making is well known to those skilled inthe art, so as suitable naturally occurring rare earth oxide mixture canbe prepared by taking an ore such as bastnaesite or monazite andpre-treating it in an appropriate manner.

It is already well known that the chemical properties of rare earthmetals and their oxides are markedly similar; I would expect that most,if not all, of the rare earth oxides -- and particularly any mixturethereof containing cerium -- give a result closely similar to theresults obtained from compositions containing cerium oxide as the solerare earth oxide.

The glass compositions of this invention consist essentially of theingredients specified above, but may be found to include also a traceamount, i.e. up to about 1%, of phosphate and/or of chlorine present asthe chloride.

Preferred embodiments of the invention, embodying the above principles,are illustrated in the following Examples 1 to 5; comparative resultsfor a modified prior art composition are illustrated in Example A.

EXAMPLE 1

A glass of the following composition was prepared and was melt drawn at1230° C:

    ______________________________________                                        Silica               50% weight                                               Sodium Oxide         10%                                                      Lithium Oxide         1%                                                      Boric Oxide           3%                                                      Titania              10%                                                      Zirconia             10%                                                      Cerium Oxide         15%                                                      Sodium Fluoride       1%                                                      ______________________________________                                    

The glass fibers obtained exhibited a tensile strength of 1.36 GPa (GigaPascals - equivalent to GN/m²).

Fibers of this composition were boiled in saturated Ca(OH)₂ for 4 hours,washed successively with water, 1% hydrochloric acid (1 minute), water,and acetone, and then dried. The strength of the fiber was increased to1.55 GPa.

EXAMPLES 2 TO 5

Glasses of various compositions as set forth in the following table weremelt drawn, and the tensile strength thereof was determined before andafter alkali treatment, with the results shown.

    ______________________________________                                        Composition      Examples                                                     % by weight      2       3       4     5                                      ______________________________________                                        SiO.sub.2        58      56      58    58                                     Li.sub.2 O       --      --      --    --                                     Na.sub.2 O       13      12      14    13                                     TiO.sub.2         9       8      10     7                                     ZrO.sub.2        12      13      13    14                                     B.sub.2 O.sub.3   3       3       4    0.5                                    CaO              --       6      --     4                                     BaO              --      --      0.1   0.6                                    CeO.sub.2         5       2      --    --                                     Naturally occurring                                                           Rare Earth Oxide mixture*                                                                      --      --      0.8   2.5                                    F                --      --      --    --                                     Cl               --      --      0.1   0.4                                    Tensile Strength (GPa)                                                        before alkali treatment                                                                        1.22    1.04    1.07  1.25                                   Tensile Strength (GPa)                                                        after alkali treatment                                                                         0.87    0.63    0.73  1.19                                   ______________________________________                                         *Obtained by treating a bastnaesite ore to remove carbonate and fluoride      ions.                                                                    

The alkali resistance of the above compositions make them eminentlysuitable for use as fibrous reinforcement in cementitious materials.They may be used in an amount up to 30% by weight of the total dryweight of cementitious materials, preferably in an amount of from 5 to10% by weight.

COMPARATIVE EXAMPLE A

I. A composition was made as disclosed in Example 2 of U.S. Pat. No.2,877,124 (which Example contains the maximum proportions of TiO₂ andZrO₂ exemplified in this patent), and to this composition an addition of4% by weight of CeO₂ was made, 4% CeO₂ being the maximum content of rareearth oxide mentioned in U.S. Pat. No. 3,127,277, to provide thefollowing glass composition:

    ______________________________________                                        SiO.sub.2          50.98 weight %                                             B.sub.2 O.sub.3     6.04                                                      Al.sub.2 O.sub.3    2.38                                                      Fe.sub.2 O.sub.3    2.97                                                      MgO                 3.60                                                      CaO                 7.40                                                      BaO                 2.80                                                      Na.sub.2 O         12.90                                                      TiO.sub.2           2.97                                                      ZrO.sub.2           3.40                                                      CeO.sub.2           4.00                                                      ______________________________________                                    

At first instance it might appear that this modified composition shouldprovide fibers of an alkali resistance equivalent to that obtained byuse of the present invention. I have found, however, that such similarproperties are not obtained as demonstrated below.

Fibers were made from this composition, and were tested for alkaliresistance, by the methods described in the preceding Examples.

The following results were obtained:

Strength before alkali treatment 0.99 GPa

Strength after alkali treatment 0.64 GPa

II. A composition as in (I) above, but containing no rare earth oxidewas formed into fibers, and these were tested, by the same methods, withthe following results:

Stength before alkali treatment 1.24 GPa

Strength after alkali treatment 0.48 GPa

The fibers exemplified in Examples 1 to 5 have strengths after alkalitreatment of from 1.04 to 1.55 GPa, which clearly shows that fibersproduced from these compositions exhibit considerably greater strengthsafter alkali treatment than can fibers produced by the modificationreferred to above. That is, fibers made in accordance with thisinvention have greater alkali resistance.

III. As a further comparison, Example 2 was repeated using 4% cericoxide; this gave fibers having a strength of 0.94 GPa before treatmentwith alkali, and 0.90 GPa after alkali treatment. Without any cericoxide a similar composition gives a strength of 0.66 GPa beforetreatment and 0.57 after alkali treatment. Thus, the percentage declinein the strength of fibers made from Example 2 composition, with orwithout ceric oxide, is less than for an Example A (I) composition withceric oxide.

Obviously, modifications may be made in the compositions of thisinvention as exemplified above. It should be noted, however, thatcertain compositions within the composition ranges of this invention maynot necessarily exhibit an especially marked increase in alkaliresistance over similar compositions not containing rare earth oxide, ormay exhibit a tendency to devitrify during fibre drawing; accordingly,the considerations and adjustments already used in glass technology toaccount for these difficulties should be applied to the invention forsuch compositions, not exemplified above, as come within the scope ofthe invention.

I claim:
 1. A glass composition, having improved chemical resistance toalkali attack, consisting essentially of:from 50 to 75 percent by weightSilica from 10 to 25 percent by weight R₂ O from .[.1.]. .Iadd.7.Iaddend.to 15 percent by weight Titania from 1 to 20 percent by weightZirconia from 0.8 to 20 percent by weight Rare Earth Oxide from 0 to 20percent by weight Boric Oxide from 0 to 10 percent by weight R¹ O from 0to 1 percent by weight Fluorine (as fluoride) from 0 to 2 percent byweight Al₂ O₃ from 0 to 1 percent by weight P₂ O₅ from 0 to 1 percent byweight Chlorine (as chloride)wherein R₂ O is selected from the groupconsisting of Na₂ O, K₂ O, mixtures thereof, and mixtures thereofcontaining up to 5% by weight lithium oxide (based on the total weightof the composition) and R¹ O is selected from the group consisting ofMgO, CaO, BaO, and SrO, and mixtures of two or more thereof.
 2. A glasscomposition according to claim 1, including not more than 30%, by weightof the titania and zirconia together.
 3. A glass composition accordingto claim 1, comprising at least 20% by weight of ZrO₂ and TiO₂ together.4. A glass composition according to claim 1, comprising at least 23% byweight of ZrO₂, TiO₂ and rare earth oxide together.
 5. A glasscomposition according to claim 1, including not more than 7% by weightof the R¹ O.
 6. A glass composition according to claim 1, wherein any ofR¹ O, fluorine Al₂ O₃, P₂ O₅ or chlorine's present in impurity amounts.7. A glass composition according to claim 1, containing not more than15% by weight of zirconia.
 8. Glass fiber having a composition asdefined in claim
 1. 9. Cementitious material, including as reinforcementtherein up to 30% by weight of glass fiber as defined in claim
 6. 10. Aglass composition consisting of:

    ______________________________________                                        Silica               50% by weight                                            Sodium Oxide         10%                                                      Lithium Oxide         1%                                                      Boric Oxide           3%                                                      Titania              10%                                                      Zirconia             10%                                                      Cerium Oxide         15%                                                      Sodium Fluoride       1%                                                      ______________________________________                                    


11. A glass composition according to claim 10, in the form of fibers.12. A glass composition consisting of:

    ______________________________________                                        Silica               58% by weight                                            Sodium Oxide         13%                                                      Titania               9%                                                      Zirconia             12%                                                      Boric Oxide           3%                                                      Ceric Oxide           5%                                                      ______________________________________                                    


13. A glass composition according to claim 12, in the form of fibers.14. A glass composition consisting of:

    ______________________________________                                        Silica               56% by weight                                            Sodium Oxide         12%                                                      Titania               8%                                                      Zirconia             13%                                                      Boric Oxide           3%                                                      Calcium Oxide         6%                                                      Ceric Oxide           2%                                                      ______________________________________                                    


15. A glass composition according to claim 14, in the form of fibers.16. A glass composition consisting essentially of:

    ______________________________________                                        Silica               58% by weight                                            Sodium Oxide         14%                                                      Titania              10%                                                      Zirconia             13%                                                      Boric Oxide           4%                                                      Barium Oxide         0.1%                                                     Mixture of naturally                                                          accuring rare                                                                 earth oxides         0.8%                                                     Cl                   0.1%                                                     ______________________________________                                    


17. A glass composition according to claim 16, in the form of fibers.18. A glass composition consisting essentially of:

    ______________________________________                                        Silica               58% by weight                                            Sodium Oxide         13%                                                      Titania               7%                                                      Zirconia             14%                                                      Boric Oxide          0.5%                                                     Calcium Oxide         4%                                                      Barium Oxide         0.6%                                                     Mixture of naturally                                                          accurring rare earth                                                          oxides               2.5%                                                     Cl                   0.4%                                                     ______________________________________                                    


19. A glass composition according to claim 18, in the form of fibres.20. A glass composition, having improved chemical resistance to alkaliattack, consisting essentially of:

    ______________________________________                                        from 50-58    percent  by  weight                                                                              Silica                                       "    11-14    "        "   "     R.sub.2 O                                    "     8-10    "        "   "     Titania                                      "    10-14    "        "   "     Zirconia                                     "    0.8-15   "        "   "     Rare Earth Oxide                             "    0.5-4    "        "   "     Boric Oxide                                  "    0.1-6    "        "   "     R.sup.1 O                                    "    0-1      "        "   "     Fluorine (as fluoride)                       "    0.1-0.4  "        "   "     Chlorine (as chloride)                       ______________________________________                                    

wherein .[.R20.]. .Iadd.R₂ O .Iaddend.is elected from the groupconsisting of Na₂ O, K₂ O, mixtures of the two, and mixtures thereofadditionally containing up to 1% by weight lithium oxide (based on thetotal weight of the composition) and R¹ O is selected from the groupconsisting of MgO, CaO, BaO, SrO and mixtures of two or more thereof.21. A glass composition according to claim 20, in the form of fibers.